Field of the Invention
The invention relates generally to the field of dentistry, and more particularly to the field of dental restorations, implants and prostheses. The invention further relates to computer assisted and conventional systems and methods for designing and manufacturing such custom dental prosthesis.
Description of Related Art
Human teeth serve a variety of functions. Not only are they important for chewing food, but they also necessary to properly pronounce certain consonants, especially fizzle- and S-sounds. Furthermore, teeth play a major role in our personal appearance. While, healthy and well aligned teeth are an ideal of beauty and appear as a cosmetic sign of youth and success.
Although various preventive measures, like frequent tooth brushing and flossing, and drinking fluoridized or iodized water are widely accepted and used, the great majority of people are sooner or later challenged with dental fillings, restorations implants, and/or prostheses.
A major goal in dentistry is to postpone loss of teeth as long as possible. Another goal is certainly to provide comfortable prostheses with a broad scope/indication and a long lasting life-time.
Generally, the number of available restorative and prosthetic options is limited. Typically fillings, inlays, and crowns are used if the root and its embedding periodontal structure are healthy, and sufficient as support for such restorative partial prostheses. Traditionally, if the original tooth can no longer be used; the use of bridges or non-customized osseointegrated implants is indicated. In this context, several negative aspects are to be endured. In order to provide the support structure for a bridge, adjacent teeth are ground, and healthy enamel is partially destroyed. Osseointegrated implants are drastically invasive and the gingiva-implant interface is often the cause of chronic local infection. Additionally, all the aforementioned restorative and prosthetic options have a limited average lifetime. Removable dentures are certainly the final prosthetic option.
When a tooth is partially damaged, either by caries or mechanical impact, the missing portion should in most cases be replaced. As long as a tooth provides enough structural strength to support a prosthesis, for example, an inlay or a crown, this will typically be the preferred solution. However, if the loss of tooth substance is severe, this may not be applicable. In these cases, a bridge can be applied, enduring the aforementioned negative consequences. Another option is to replace the tooth with an implant.
There are many methods or options for replacing missing teeth. Off-the-shelf or pre-shaped osseointegrated dental implants are one of the options. Osseointegration means the direct contact of the implant surface with the bone without a fibrous connective tissue interface (natural teeth are typically not in direct contact with the bone, but are connected to the bone by ligaments). The use of such dental implants includes a wide variety of implant designs and materials, use of implants in different locations in the mouth and use of a variety of surgical protocols.
Endosteal implants are placed into the bone, like natural tooth roots. They can provide an anchor for one or more artificial teeth. They are the most commonly used type of implants. There are various types of endosteal implants, for example, screws, cylinders, cones, plates and blades. The generic screw, cylinder and cone types of implants are sometimes called “root-form” type. Such generic root-form implants that replace a single tooth generally consist of three parts, the actual implant-root for osseointegration, an abutment and the artificial crown. The interfaces between the three aforementioned parts are critical in respect to the sealing quality between said three parts. Bacterial infections can be caused if the sealing is compromised in regards to its short, mid and long-term stability.
Sometimes implant designs that actually consolidate two of said three parts, for example, the implant-root to be osseointegrated and the abutment, are referred to as one-piece implants.
Such three-part implant designs have a first sub-gingival joint between the implant screw and the abutment. The first joint is in its height placed adjacent to the bone crest of the jaw of the implant-receiving patient. The second joint is placed iso- or supra-gingival, which means on the same vertical height of the mouth facing surface of the gingiva or beyond the trans-gingival portion of the overall implant design. The first joint between the implant screw and abutment is especially under the static and dynamic stress of mastication forces, and is exposed as an area where bacteria may congregate, causing a chronically infection.
Contrary hereto, the term “one-piece” implant as used hereinafter is meant to refer to the integration of all three parts: the implant root, the abutment, and the crown. The term “immediate placing” of an implant is used if the integration of the implant into the bone occurs a short term after the extraction of a tooth. If such implants have a reasonable initial contact stability with the bone directly after being inserted, the so called primary stability, then such implants are called “immediately loaded”, which means that the osseo-integrative stability, the so called secondary stability, does not need to be developed before performing the following process steps: making an impression of the abutment part of the implant in conjunction with the gingiva and the adjacent teeth situation, then fabricating the crown, implementing the crown, and actually allowing the patient to use the implant for mastication.
Subperiosteal implants are implants that are placed over the bone in cases where the bone has atrophied and jaw structure is limited. Subperiosteal implants are customized metal frameworks, providing the equivalent of multiple tooth roots. They can be applied in a limited area or in the entire mouth. After application, natural tissue membrane or bone will grow back around the implant, thus providing more stability. Posts protrude through the gum to hold the prosthesis.
Traditionally, osseointegrated dental implants are placed in bone and covered by mucosa during the immediate post-operative healing period. At four to eight months, a second surgical procedure is performed to expose the implant so it may be loaded with various types of dental crowns. In recent years, immediate implant placement following tooth extraction and immediate crown loading after surgical placement has become more common.
Generic ceramic dental implants are available made from yttrium-stabilized zirconia ceramics. Although such ceramic materials are due to its internal crystal structure and mechanisms able to suppress micro-cracks, it has been reported that in the moist-warm environment of the human body the long term stability of yttrium-stabilized zirconia ceramics is compromised to the extent that respective dental implants cannot be considered fracture-safe for the life-time expectations established in the industry.
However, the success rate and the in-vivo life time of osseointegrated dental implants are limited, and the surgical procedure is heavily invasive, because the bone needs to be drilled or ground in order to be adapted to the shape of the non-customized implants. Furthermore, osseointegrated implants are a limiting factor in a later orthodontic treatment. Problems relating to nerve transposition, osseous grafting, ridge augmentation, and sinus augmentation of osseointegrated dental implants, and/or to tissue health adjacent to dental implants have also been reported. Patients often complain about chronically infected periodontal structure caused by osseointegrated implants.
In cases where a tooth is not severely damaged, and would be ready to receive a partial restoration, but an intra-oral repair is impossible due to access problems, or a reverse root canal treatment is required, an alternative method is the intentional re-implantation. The tooth is extracted, repaired, and re-integrated into the existing periodontal structure of a dental patient. Nuzzolese et al. wrote in the Journal of Contemporary Dental Practice, Volume 5, No. 3, Aug. 15, 2004: “It is well known dental reimplantation is indicated following traumatic avulsion by the preservation of cellular vitality in the periodontal ligament and under conditions of asepsis. The rate of endodontic success at five years reported in the literature ranges between 70% and 91%. However, intentional dental reimplantation is an effective strategy for the treatment of teeth that would be difficult, if not impossible, to treat using traditional root canal therapy. Different prognoses exist for intentional dental reimplantation and trauma-related reimplantation. This is due to such important variables such as the level of cellular vitality in the periodontal ligament; the degree of trauma to surrounding tissues, and the degree of asepsis when a tooth is removed. Surgical extraction is more favorable in this regard compared to a traumatic avulsion scenario.” Although this method is not yet widely used, the reported success rates are noteworthy. Reported are also autogenous and allogenic transplantation of a healthy natural tooth into the extraction socket for parodontal/periodontal integration. A disadvantage relating to all such techniques is certainly that the specific tooth to be reimplanted or transplanted still needs an overall reasonable condition and prognosis to justify an intentional re-implantation and that only certain root and root canal deficiencies can be repaired this way.
Various publications reporting that the prognosis of intentional reimplanted or transplanted teeth is significantly better than the reimplantation after a traumatic extraction, since the extraction is surgically controlled and relatively aseptic techniques are utilized. Spouge writes in his Oral Pathology, Mosby, Saint Louis 1973; “The majority of reimplantations however are clinically successful, and the teeth are retained firmly in the socket for the appropriate 5 year period. However, despite the apparent success, most of them show localized ankylosis and gross resorption of the root at the end of this time. The fibrous attachment that develops in the new periodontal ligament area often involves the formation of an immature type of connective tissue whose fibers remain tangential to the root surface rather than becoming physiologically oriented. There is experimental evidence to suggest that formation of a physiologic periodontium is more easily achieved in condition where the viability of the original periodontal ligament is maintained . . . . In keeping with this, the prognosis for clinical success in a reimplanted tooth fall rapidly if is have been completely dislocated from its socket for more than 24 hours.” Wong suggests in Quintessence International, Vol. 33. No. 2, 2002 a surgical “exarticulation” method, where the removal of the tooth from its socket is achieved “(after the incision of the crestal periodontal ligament fibers with micro-blades) with a combination of luxation and gentle, rotary, reciprocating movements” in order to minimize physical trauma to the excising periodontium. Goerig et al. recommends in Quintessence International, Vol. 19, No. 8, 1988 a sectioning procedure where a molar tooth is cut in half dividing the roots in order to minimize the damage of the existing periodontal ligament. The Ogram System (www.ogramsystem.com) provides a tooth removal protocol promising no or very little trauma of the surrounding tissue.
EI-Bialy et al. from the University of Alberta, Canada report the stimulation of jaw growth and tissue healing by directly applying ultrasound vibes to the tooth of interest. In this context it is known to those skilled in the art that the alternating “load” of dental structures in patients' day-to-day use of their dentition activates healing processes while a protection against or the avoidance of such alternating load causes resorption of roots, bone and soft tissue.
U.S. Pat. No. 5,562,450 references as prior art the German application DE 27 29 969 A1, which is incorporated herein by reference in its entirety, describing the osseointegration of an implant that is substantially a copy of an extracted human tooth fabricated by a process involving copy milling. In order to be successfully osseointegrated the connective tissue (e.g., ligament) remaining in the extraction socket needs to be removed by being scraped out or curetted. The '450 patent recognizes the need to create a compression pressure between the bone and the implant in order to reach reasonable primary stability of the implant and teaches therefore to dimensionally enlarge the anatomical shape of the implant over the extracted tooth to fill the extraction socket.
Rubbert and Berndt reference in the article “Topologically Structured Surfaces and Coating Treatments for Periodontal and Osseo-Integration” published on Apr. 7, 2009, which is incorporated herein by reference in its entirety, various aspects of surface condition and treatments of dental implants and prostheses.
U.S. Pat. No. 6,099,313 discloses a dental implant for osseointegration having a bone-contact section which is root-shaped with an apical extension and an abutment described as a build-up section for fastening a crown.
All such restorative and prosthetic options and methodologies are deficient—being heavily invasive and/or limited in their respective scope. There has not been recognition, until now by the inventors, of the need for a product, systems, and methods related to the integration of dental prosthesis such as artificial tooth, bridges, or segments of the dentition that includes (a) custom-shaped root structures to be osseointegrated as one piece, (b) custom-made positioning and fixation splints for achieving primary stability, and (c) even more beneficial, parts to be integrated into the existing periodontal structure of an individual patient, having the desirable broad scope and reduced invasive requirements. There is also no prior recognition of fabricating the root-shaped custom portions of the prosthesis based on anatomical imaging data prior to the extraction of the tooth or of the teeth of interest or directly of the alveolar situation.
In addition, the inventors disclose the use of advanced ceramic materials, manufacturing technologies to increase the density of ceramic materials to its theoretical degree to be considered fracture-safe for use as dental implants or prostheses, metal-ceramic diffusion bonding technologies to overcome bacterial issues developing on the sub-gingival joints of traditional 3-part implant designs, and tissue engineering methods for osseo-integration and perio-type integration to enhance the clinical integration of prostheses designed and manufactured according to the inventions disclosed herein as further advantageous embodiments not previously recognized until now.
The product, and related systems and methods provided by embodiments of the present invention or inventions comprise several independent inventive features providing substantial improvements to prior art. The greatest benefit will be achieved for dental treatments—especially for patients requiring tooth replacement.